This invention relates to an apparatus for monitoring the condition of bulk or flowable material.
It is desirable from the point of view of economic and environmental protection to repeatedly use, for example, molding sand rather than storing it in waste dumps after a single use. Before reuse, however, the used sand has to be regenerated, that is, it has to be cleaned to remove old bentonite contents. The quality of regeneration has to be continuously monitored to ensure that the cleaning process follows an optimum course. By adding fresh bentonite the regenerated sand regains its form-retaining properties.
The essential component of bentonite is montmorillonite -- Al.sub.2 (Si.sub.4 O.sub.10) (OH).sub.2 nH.sub.2 O -- which excels by its particularly superior swelling properties and dispersibility. The aluminum contents (approximately 10%) permits the monitoring of the progress of the regeneration process by means of an aluminum anaylsis. Expediently, approximately every 15 minutes an analysis value should be obtained to ensure that the analyzing process has an at least quasi-continuous course. Further, the sample taken has to be sufficiently representative (several kg per measurement) in order to maintain sampling errors at a small value. The concentration range of interest is between 1 and 10% bentonite (corresponding to 0.1 and 1% aluminum). The temperature of the sand is above 100.degree. C.
It has not yet been known to utilize the neutron activation analysis with a Cf-252 neutron source for an on-line analyzing process of solid materials in industrial process monitoring. According to this method, concentrations of predetermined components in the flowing material can be determined and the processes can be accordingly controlled. It is an advantage of this method that it can be performed without destruction of the samples and through the walls of tubes that guide the flowing material so that no scooping of samples from the material flow is necessary. Aluminum is well adapted for the process analysis because the radionuclide Al-28 has a short half-life of 2.3 minutes and a relatively high gamma energy of 1.78 MeV.